1. Technical Field
The present invention relates to a donor substrate for a full-color organic electroluminescent display device, a method of manufacturing the same, and a full-color organic electroluminescent display device using the donor substrate. More particularly, the present invention relates to a donor substrate for a full-color organic electroluminescent display device, a method of manufacturing the same, and a full-color organic electroluminescent display device using the donor substrate, in which a transfer donor substrate, which is used upon forming an emission layer for the full-color organic electroluminescent display device, is patterned such that misalignment does not occur upon forming the emission layer.
2. Related Art
Generally, an organic electroluminescent (EL) display device is composed of several layers, such as an anode, a cathode, a hole injecting layer, a hole transporting layer, an emission layer, an electron transporting layer, and an electron injecting layer. Organic electroluminescent display devices are classified into polymer organic electroluminescent display devices and small molecule organic electroluminescent display devices according to the material used therein. Typically, in the case of the small molecule organic electroluminescent display device, each of the layers is deposited by a vacuum deposition process, and in the case of the polymer organic EL device, the electroluminescent (EL) element is manufactured by a spin coating process.
For monochrome devices, an organic electroluminescent display device using a polymer may be simply manufactured by a spin coating process and needs a lower driving voltage compared to a device using the small molecules, but has the disadvantages of efficiency degradation and life span degradation. Furthermore, when manufacturing full color devices, polymers of red, green and blue colors have to be patterned, which degrades luminescence properties, such as efficiency and life span, when an inkjet technique or a laser induced thermal imaging process is used for the patterning.
In particular, when the laser induced thermal imaging process is used for patterning, a non-transferred material is primarily used as a single polymer material. A method of forming a pattern of a polymer organic electroluminescent display device using a laser induced thermal imaging process is disclosed in Korean Patent Application No. 1998-51844, and also in U.S. Pat. Nos. 5,998,085, 6,214,520 and 6,114,088.
The application of the laser induced thermal imaging process requires at least a light source, a transfer film, and a substrate, wherein light emitting from the light source is absorbed into a light absorption layer of a transfer layer and is converted to thermal energy, and wherein the thermal energy allows a material forming the transfer layer to be transferred onto the substrate, so that a desired image is formed (see U.S. Pat. Nos. 5,220,348, 5,256,506, 5,278,023 and 5,308,737).
This laser induced thermal imaging process has been used to manufacture a color filter for a liquid crystal display device, and has been also used to form a pattern of an electroluminescent material (see U.S. Pat. No. 5,998,085).
U.S. Pat. No. 5,937,272 discloses a method of forming an advanced patterned organic layer in a full-color organic electroluminescent display device. The method uses a donor support which is coated with a transferable coating material of an organic electroluminescent material. The donor support is heated to cause the organic electroluminescent material to be transferred onto a recessed surface of a substrate that forms a colored organic EL medium in intended sub-pixels. At this time, heat or light is applied to the donor substrate so that the electroluminescent material is vaporized and transferred to the pixel.
U.S. Pat. No. 5,688,551, a sub-pixel is formed in each pixel region by transfer from a donor sheet to a receiver sheet. In a transfer process, a sublimate organic electroluminescent material is transferred from the donor sheet to the receiver sheet at a low temperature (e.g., about 400° C. or less) to form the sub-pixel.
When the organic layer is a small molecule layer, the pattern is not clean, and when it is a polymer layer, the pattern is also not clean because the portion that must be transferred and patterned is left on the donor substrate when the interlayer adhesive strength is larger than the adhesive strengths.